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| 1. Are asphalt plants dirty and bad for the environment? |
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The asphalt industry works hard to be a good citizen. It has spent millions of dollars to develop the most advanced technology to keep the environment in their communities clean. Asphalt plants have adopted stringent emission standards that exceed those of the EPA. Emission control systems also trap and remove fine sand and dust particles. As a result, the EPA has deleted asphalt plants from its list of major sources of hazardous air pollutants.
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| 2. Are there hazardous materials at an asphalt facility? |
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Liquids that must be handled with care at a Hot Mix Asphalt facility are: 1) fuel oil for the burner, which is the same kind of fuel oil you may be using to heat your home; 2) fuel for vehicles, which the same product you buy at the gas station; and 3) at some facilities, solvents for the quality control lab. These solvents are used in small quantities with great care, and new lab procedures are quickly making solvents obsolete.
By federal law, a Hot Mix Asphalt facility must keep these products, including the fuel oil, either in underground tanks that meet strict EPA standards, or in above-ground tanks surrounded by berms that would hold ALL the contents in the event of a spill.
Even if there were a spill or leak, Asphalt Cement starts to harden the moment it cools. Unless it’s 250 degrees Fahrenheit outside, it simply cannot travel over the ground more than a few feet. It will not penetrate the soil more than an inch or two before solidifying. Asphalt Cement does not mix with, or become soluble, in water.
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3. Can asphalt pavement be recycled?
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Yes! Asphalt pavement is 100 percent recyclable and can be made to perform better the second or even third time around. In fact, it is the most recycled product in the United States, both in terms of tonnage (73 million tons, more than any other material) and in terms of percentage (80 percent of reclaimed asphalt pavement is recycled, a higher percentage than any other substance). That compares to significantly lower percentages for aluminum cans, newsprint, plastic and glass beverage containers, and magazines. Asphalt roads are removed, recrushed, mixed with additional aggregate and fresh asphalt cement, remixed and placed back on the road. The hot mix asphalt industry also uses the following recycled materials: slag from the steel-making process, roofing shingles, sand from metal-casting foundries, and rubber from old tires.
In a joint report to Congress, the Federal Highway Administration and the Environmental Protection Agency estimated that more than 73 million tons of asphalt paving material was recycled in 1992.
Recycling roads not only conserves natural resources and decreases construction time, it saves American taxpayers more than $300 million each year.
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| 4. How environmentally safe are asphalt plants? |
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Asphalt plants must meet rigorous standards established by the EPA and other agencies, but often the individual plants set their own standards that are even more demanding. Recent improvements in asphalt production have made the industry even more environmentally friendly. In fact, after a six-year study, the EPA announced in 2002 that asphalt plants are no longer on its list of industries considered major sources of hazardous air pollutants.
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| 5. Is asphalt a sustainable material? |
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Clearly, it is. In addition to its recyclability, which conserves precious natural resources, asphalt provides long-life solutions for pavement construction. Some asphalt pavements reduce noise pollution and alleviate other environmental concerns. And, while annual production of asphalt paving material has increased by more than 250 percent over the past 40 years, emissions from asphalt plants have dropped by 97 percent or more. Some additional points to consider:
Asphalt is not soluble or harmful in a water environment. It has been used successfully for many years in fish hatcheries, reservoirs of drinking water for human consumption, and other environmental protection applications.
Asphalt prevents pollution from getting into water supplies and protects against disease from waste materials. It can be combined with aggregate to form a voidless and impermeable layer. Asphalt pavements are effective liners and caps for landfills.
Many states have tested discarded asphalt pavement and determined that it should be categorized as clean fill.
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| 6. What is Warm Mix Asphalt? |
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What is Warm Mix Asphalt (WMA)? How is it different from Hot Mix Asphalt (HMA)? In the simplest of terms, warm mix asphalt is the combination of aggregates and liquid asphalt, just like hot mix asphalt. However, WMA requires less heat to produce than HMA due to the incorporation of an additive to the mixing process. These additives, of which there are currently four on the market, appear to reduce the viscosity of the liquid asphalt at a given temperature. As a result, the liquid asphalt coats the aggregates at reduced temperature compared to HMA.
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History
Although efforts to reduce mixing temperatures have been underway since the 1970s in the United States, the warm mix asphalts movement of today started in Europe. The European Union has made a commitment to significantly reduce greenhouse gases produced as a result of manufacturing. One area of focus in meeting these reduction goals was the hot mix asphalt industry. That industry has been building asphalt pavements with WMA technology for several years. WMA activity in the United States to date has occurred through test projects throughout the country.
Benefits
Warm mix asphalt has the potential to allow the producers of hot mix asphalt to lower the temperatures at which the material is mixed and placed on the project. To date, documented reductions in temperature during production have ranged from 30 to 100 degrees Fahrenheit. These reductions in heat required to produce the mix mean less fuel is used and consumed, fewer greenhouse gases are produced and emissions are reduced. This could be especially beneficial in ozone non-attainment areas where the reduction of emissions is essential in the effort to get into compliance with the Clean Air Act.
In addition, WMA may provide the contractor greater latitude in terms of the turnaround time for placing the mixed asphalt after it has left the plant. Given that WMA has a lower temperature than HMA to begin with, it takes longer to cool off than HMA.
Additives
There are currently four technologies on the market which are used to produce warm mix asphalt:
Aspha-Min (www.aspha-min.com)
WAM-Foam (www.wamfoam.com)
Sasobit (http://www.sasolwax.com/Sasobit_Technology.html)
Evotherm (www.evotherm.com) To learn more about these products and their role in the production of WMA, you can click on each product name and connect to the company website for that product.
Future
In exploring whether warm mix asphalt is the wave of the future, the following questions must be addressed:
Can WMA pavements be opened to traffic as quickly as HMA pavements after construction?
What are the performance characteristics of these pavements?
In the case of technologies developed in other, can they be adapted to the U.S. where climate conditions are often more extreme?
Since the production temperature is lower does the binder not age as much?
Will there be a reduction in the potential for thermal cracking?
Will there be a difference in the potential for rutting?
Will the contractor have to use a different grade of binder?
Will there need to be changes for the mix design procedure?
Will the performance-graded binder in a warm mix perform differently from pavements produced at a higher temperature? |
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| 7. Why are so many asphalt plants necessary? |
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| Asphalt pavement material begins to cool as soon as it is mixed. In order to maintain workability at the paving site, and for the highest quality of the finished pavement, the mixing facility (asphalt plant) must be near the paving site. |
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| 8. Will an asphalt plant in my community be a nuisance? |
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More than 30 years ago, Hot Mix Asphalt facilities often generated noticeable levels of dust, smoke, odors, and noise. But two things have brought big changes. One was the EPA’s New Source Performance Standards, which went into effect in 1973. These required HMA producers to pass strict emission standards and install control systems to prevent the release of dust and smoke into the air. A facility must also meet stringent “visible emissions” tests in order to comply with regulations. EPA now acknowledges that HMA facilities are not a major source of emissions.
An even stronger incentive for clean operation is economic. It’s in the owner’s best interest to make sure that all the equipment is operating at peak efficiency – which means producing very little in the way of emissions.
Hot Mix Asphalt producers want to be good neighbors. They strive to build clean, quiet facilities compatible with the rest of the neighborhood.
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